Stocking neon gobies

Question
Hi.
I'd like to know how many neon gobies i can house on my 100gallon reef tank? It has been running a little bit over 3 years and i recently bought a hippo tang (dory) and it was scratching on the LR and now almost all my fish are doing the same. I know it isn't ich because none of them have white spots or anything like that. The fish i have are
1purple tang
1sailfin tang
1yellow tang
1 one-spot foxface fish
a male-female pair of maroon clownfish (have spawned already many times)
and 1long nose butterfly fish.
So again how many neon gobies could i put on the tank so they will provide a good service but not feel too crowded?
Thanks in advance !!!

Answer
Hey Aldo,
It can take a while for the ich spots to show in the crystaline form. So keep a close eye on things. The rule of thumb is 1 inch of fish per gallon based on the adult size the fish can become. Most of the gobies you are thinking of grow to between 2 and 3 inches. So you can see the math there. I personally would not add more than 4 or 6 though. That shoud be sufficient with your population. Let me know if this helps.